Various methods and apparatuses for aperturing, deforming, and/or stretching webs are disclosed in the patent literature. With an aperturing method such as rotary knife aperturing, it is difficult to produce a web having closely-spaced apertures wherein the apertures have desirable widths in the cross-machine direction (“CD”). In order to space aperture rows close together, activation teeth may be provided which have a very small included angle. However, this approach poses a problem because apertures are produced which do not have sufficient aperture width in the CD, even at high engagement depths (the interference of an activation tooth roll with a mating ring roll). The resultant apertures are often elongated in the machine direction—leading to a slit-like appearance, low open area, and potential stress concentrations which cause in-use tearing. Creating slit-like, low-open-area apertures is particularly problematic as tougher and more tear-resistant webs are utilized. Rounded or tapered hot-pin aperturing is common, but has the drawback of requiring greater registration precision for the mating rolls, and it typically results in greater aperture spacing. Rounded or tapered hot-pin aperturing is typically run at lower linear speeds.
Post ring-rolling an apertured web to stretch it is possible, but can result in alternating rows of aperture sizes since apertures cannot be lined up with the subsequent ring roll stretching process. It is difficult to align features in the cross direction with later processes due to variable spreading of the substrate. Post ring-rolling can also significantly weaken the web, making it more prone to tearing.
It is desirable to produce a web having discrete, closely-spaced apertures wherein the apertures have larger CD widths than previously possible. A need exists for an apertured web which is stronger in the cross-machine direction so it doesn't easily tear in the cross-machine direction. A need exists for a method of producing an apertured web having larger, wider, more open apertures. A need also exists for apparatuses that will allow a web to be apertured with the apertures having desired, larger-widths in the cross-machine direction.
There are many known processes for creating a web with ridges and grooves, for example ring rolling. There are also many know processes for creating a web with apertures, for example, hot pin aperturing. However, it is difficult to produce a corrugated web having alternating ridges and grooves which are registered to a specific aperture pattern. Processes exist for micro-aperturing followed by ring-rolling; however, this results in flattened webs with no corrugation. A web with ridges and grooves (flat strips) may be formed via air-jetting or water jetting on a patterned belt. However, air-jetting or water jetting are much slower processes and requires more energy than the invention described herein. In addition, the ridges are not hollow and can retain more fluid.
It is desirable to produce a web having alternating ridges and grooves wherein apertures are located in specific positions in the web, for instance, in the grooves or in the ridges. A need exists for an apertured web which comprises a registered corrugation pattern.
These are all goals of the present invention; embodiments described herein may achieve various combinations of these goals. A particular embodiment may, but need not, embody every goal.